If $3a + 9b = 3$ and $7x + 3y + 3z = -6$, what is $-18b - 6a - 18z - 18y - 42x$ ?
Answer: $= -6a - 18b - 42x - 18y - 18z$ $= (-2) \cdot (3a + 9b) + (-6) \cdot (7x + 3y + 3z)$ $= (-2) \cdot (3) + (-6) \cdot (-6)$ $= -6 + 36$ $= 30$